The present invention provides an ethylene/tetrafluoroethylene copolymer showing good heat resistance and good crack resistance even in a high temperature environment. The present invention is an ethylene/tetrafluoroethylene copolymer, comprising: copolymerization units derived from ethylene; tetrafluoroethylene; and a fluorine-containing vinyl monomer represented by general formula: CH2═CH—Rf in the formula, Rf representing a perfluoroalkyl group containing four or more carbon atoms, a fluorine-containing vinyl monomer content being 0.8 to 2.5 mol % to a total amount of all monomers, an ethylene/tetrafluoroethylene molar ratio being 33.0/67.0 to 44.0/56.0, a CH index being 1.40 or less, a melting point being 230° C. or higher, and a melt flow rate being 40 (g/10 minutes) or less.